GNU Astronomy Utilities

7.4.5.3 MakeCatalog output columns

The final group of options particular to MakeCatalog are those that specify
which columns should be written into the final output table. For each
column there is an option, if it has been called on the command line or in
any of the configuration files, it will included as a column in the output
catalog in the same order (see Configuration file precedence). Some
of the columns apply to both objects and clumps and some are particular to
only one of them. The latter cases are explicitly marked with [Objects] or
[Clumps] to specify the catalog they will be placed in.

--i

--ids

This is a unique option which can add multiple columns to the final
catalog(s). Calling this option will put the object IDs (--objid)
in the objects catalog and host-object-ID (--hostobjid) and
ID-in-host-object (--idinhostobj) into the clumps catalog. Hence
if only object catalogs are required, it has the same effect as
--objid.

--objid

[Objects] ID of this object.

-j

--hostobjid

[Clumps] The ID of the object which hosts this clump.

--idinhostobj

[Clumps] The ID of this clump in its host object.

-x

--x

The flux weighted center of all objects and clumps along the first FITS
axis (horizontal when viewed in SAO ds9), see \(\overline{x}\) in
Measuring elliptical parameters. The weight has to have a positive
value (pixel value larger than the Sky value) to be meaningful! Specially
when doing matched photometry, this might not happen: no pixel value might
be above the Sky value. For such detections, the geometric center will be
reported in this column (see --geox). You can use
--weightarea to see which was used.

-y

--y

The flux weighted center of all objects and clumps along the second FITS
axis (vertical when viewed in SAO ds9). See --x.

--geox

The geometric center of all objects and clumps along the first FITS
axis axis. The geometric center is the average pixel positions
irrespective of their pixel values.

--geoy

The geometric center of all objects and clumps along the second FITS
axis axis, see --geox.

--minx

The minimum position of all objects and clumps along the first FITS axis.

--maxx

The maximum position of all objects and clumps along the first FITS axis.

--miny

The minimum position of all objects and clumps along the second FITS axis.

--maxy

The maximum position of all objects and clumps along the second FITS axis.

--clumpsx

[Objects] The flux weighted center of all the clumps in this
object along the first FITS axis. See --x.

--clumpsy

[Objects] The flux weighted center of all the clumps in this
object along the second FITS axis. See --x.

--clumpsgeox

[Objects] The geometric center of all the clumps in this object along
the first FITS axis. See --geox.

--clumpsgeoy

[Objects] The geometric center of all the clumps in this object along
the second FITS axis. See --geox.

-r

--ra

Flux weighted right ascension of all objects or clumps, see
--x. This is just an alias for one of the lower-level
--w1 or --w2 options. Using the FITS WCS keywords
(CTYPE), MakeCatalog will determine which axis corresponds to the
right ascension. If no CTYPE keywords start with RA, an error
will be printed when requesting this column and MakeCatalog will abort.

-d

--dec

Flux weighted declination of all objects or clumps, see --x. This
is just an alias for one of the lower-level --w1 or --w2
options. Using the FITS WCS keywords (CTYPE), MakeCatalog will
determine which axis corresponds to the declination. If no CTYPE
keywords start with DEC, an error will be printed when requesting
this column and MakeCatalog will abort.

--w1

Flux weighted first WCS axis of all objects or clumps, see
--x. The first WCS axis is commonly used as right ascension in
images.

--w2

Flux weighted second WCS axis of all objects or clumps, see
--x. The second WCS axis is commonly used as declination in
images.

--geow1

Geometric center in first WCS axis of all objects or clumps, see
--geox. The first WCS axis is commonly used as right ascension in
images.

--geow2

Geometric center in second WCS axis of all objects or clumps, see
--geox. The second WCS axis is commonly used as declination in
images.

--clumpsw1

[Objects] Flux weighted center in first WCS axis of all clumps in this
object, see --x. The first WCS axis is commonly used as right
ascension in images.

--clumpsw2

[Objects] Flux weighted declination of all clumps in this object, see
--x. The second WCS axis is commonly used as declination in
images.

--clumpsgeow1

[Objects] Geometric center right ascension of all clumps in this object,
see --geox. The first WCS axis is commonly used as right ascension
in images.

--clumpsgeow2

[Objects] Geometric center declination of all clumps in this object, see
--geox. The second WCS axis is commonly used as declination in
images.

-b

--brightness

The brightness (sum of all pixel values), see Flux Brightness and magnitude. For clumps, the ambient brightness (flux of river pixels around
the clump multiplied by the area of the clump) is removed, see
--riverflux. So the sum of all the clumps brightness in the clump
catalog will be smaller than the total clump brightness in the
--clumpbrightness column of the objects catalog.

If no usable pixels (blank or below the threshold) are present over the
clump or object, the stored value will be NaN (note that zero is
meaningful).

--brightnesserr

The (\(1\sigma\)) error in measuring the brightness of objects or
clumps.

--clumpbrightness

[Objects] The total brightness of the clumps within an object. This is
simply the sum of the pixels associated with clumps in the object. If no
usable pixels (blank or below the threshold) are present over the clump or
object, the stored value will be NaN, because zero (note that zero is
meaningful).

--brightnessnoriver

[Clumps] The Sky (not river) subtracted clump brightness. By definition,
for the clumps, the average brightness of the rivers surrounding it are
subtracted from it for a first order accounting for contamination by
neighbors. In cases where you will be calculating the flux brightness
difference later (one example below) the contamination will be (mostly)
removed at that stage, which is why this column was added.

One example might be this: you want to know the change in the clump flux as
a function of threshold (see --threshold). So you will make two
catalogs (each having this column but with different thresholds) and then
subtract the lower threshold catalog (higher brightness) from the higher
threshold catalog (lower brightness). The effect is most visible when the
rivers have a high average signal-to-noise ratio. The removed contribution
from the pixels below the threshold will be less than the river
pixels. Therefore the river-subtracted brightness (--brightness)
for the thresholded catalog for such clumps will be larger than the
brightness with no threshold!

If no usable pixels (blank or below the possibly given threshold) are
present over the clump or object, the stored value will be NaN (note that
zero is meaningful).

--mean

The mean sky subtracted value of pixels within the object or clump. For
clumps, the average river flux is subtracted from the sky subtracted
mean.

--median

The median sky subtracted value of pixels within the object or clump. For
clumps, the average river flux is subtracted from the sky subtracted
median.

-m

--magnitude

The magnitude of clumps or objects, see --brightness.

-e

--magnitudeerr

The magnitude error of clumps or objects. The magnitude error is calculated
from the signal-to-noise ratio (see --sn and Quantifying measurement limits). Note that until now this error assumes uncorrelated
pixel values and also does not include the error in estimating the aperture
(or error in generating the labeled image).

For now these factors have to be found by other means.
Task 14124 has been
defined for work on adding these sources of error too.

--clumpsmagnitude

[Objects] The magnitude of all clumps in this object, see
--clumpbrightness.

--upperlimit

The upper limit value (in units of the input image) for this object or
clump. See Quantifying measurement limits and Upper-limit settings for a complete explanation. This is very important for the
fainter and smaller objects in the image where the measured magnitudes are
not reliable.

--upperlimitmag

The upper limit magnitude for this object or clump. See Quantifying measurement limits and Upper-limit settings for a complete
explanation. This is very important for the fainter and smaller objects in
the image where the measured magnitudes are not reliable.

--upperlimitonesigma

The \(1\sigma\) upper limit value (in units of the input image) for
this object or clump. See Quantifying measurement limits and
Upper-limit settings for a complete explanation. When
--upnsigma=1, this column’s values will be the same as
--upperlimit.

--upperlimitsigma

The position of the total brightness measured within the distribution of
randomly placed upperlimit measurements in units of the distribution’s
\(\sigma\) or standard deviation. See Quantifying measurement limits and Upper-limit settings for a complete explanation.

--upperlimitquantile

The position of the total brightness measured within the distribution of
randomly placed upperlimit measurements as a quantile (value between 0 or
1). See Quantifying measurement limits and Upper-limit settings
for a complete explanation. If the object is brighter than the brightest
randomly placed profile, a value of inf is returned. If it is less
than the minimum, a value of -inf is reported.

--upperlimitskew

This column contains the non-parametric skew of the sigma-clipped random
distribution that was used to estimate the upper-limit magnitude. Taking
\(\mu\) as the mean, \(\nu\) as the median and \(\sigma\) as
the standard deviation, the traditional definition of skewness is defined
as: \((\mu-\nu)/\sigma\).

This can be a good measure to see how much you can trust the random
measurements, or in other words, how accurately the regions with signal
have been masked/detected. If the skewness is strong (and to the positive),
then you can tell that you have a lot of undetected signal in the dataset,
and therefore that the upper-limit measurement (and other measurements) are
not reliable.

--riverave

[Clumps] The average brightness of the river pixels around this
clump. River pixels were defined in Akhlaghi and Ichikawa 2015. In
short they are the pixels immediately outside of the clumps. This
value is used internally to find the brightness (or magnitude) and
signal to noise ratio of the clumps. It can generally also be used as
a scale to gauge the base (ambient) flux surrounding the clump. In
case there was no river pixels, then this column will have the value
of the Sky under the clump. So note that this value is not sky
subtracted.

--rivernum

[Clumps] The number of river pixels around this clump, see
--riverflux.

-n

--sn

The Signal to noise ratio (S/N) of all clumps or objects. See Akhlaghi
and Ichikawa (2015) for the exact equations used.

--sky

The sky flux (per pixel) value under this object or clump. This is
actually the mean value of all the pixels in the sky image that lie on
the same position as the object or clump.

--std

The sky value standard deviation (per pixel) for this clump or
object. Like --sky, this is the average of the values in the
input sky standard deviation image pixels that lie over this object.

-C

--numclumps

[Objects] The number of clumps in this object.

-a

--area

The raw area (number of pixels) in any clump or object independent of what
pixel it lies over (if it is NaN/blank or unused for example).

--clumpsarea

[Objects] The total area of all the clumps in this object.

--weightarea

The area (number of pixels) used in the flux weighted position
calculations.

--geoarea

The area of all the pixels labeled with an object or clump. Note that
unlike --area, pixel values are completely ignored in this
column. For example, if a pixel value is blank, it won’t be counted in
--area, but will be counted here.